Preschool overload

Not too long ago, my 11-year-old brother asked me if I was going to put Noogs (3) in preschool. This seemed like an odd question coming from a boy who, until last year, was homeschooled all his life, and it made me think of the prevalence of the assumption that formal schooling must begin earlier and earlier. I'm certainly not in the "Reading by Nine!" category (I think the LA Times ran an ad campaign or a school-related initiative under that title a while back), but I don't think that preschool is the most effective educational strategy for the under-five set. I've been thinking a lot about this lately, as Noogs reaches the age where she's getting interested in writing and reading, and I'd appreciate any thoughts anyone might care to offer on the subject.

Full disclosure: A few months ago I told an editor at Heart and Mind magazine that I'd work on an article about preschooling, and for various reasons, most more trivial than some, I've not started. So I'm looking for ideas to jump-start the process, because as in college, I can't write if I'm staring a deadline in the face.